The application of assisted or "artificial respiration" is an absolute lifesaving necessity when breathing ability is compromised or otherwise interfered with by coma, drug-induced depression, or acute pulmonary disease. Under these life-threatening conditions and during anesthesia, patients are ventilated by mechanical respirators which inflate the lungs. Oxygen is delivered to the lungs through a flexible plastic conduit (endotracheal tube), which connects the respirator the windpipe. The oropharyngeal passage is curved and narrow, and the vocal cords and glottic opening often cannot be seen even with a tongue depressor. Specifically, the relationship of the epiglottis to the glottic opening is such that during endotracheal intubation it is necessary to move the epiglottis to expose the glottic opening. The insertion of an endotracheal tube is a difficult and often dangerous procedure which requires the use of an instrument called a laryngoscope. The procedure in which a laryngoscope is used by a physician to manipulate the tongue and the epiglottis to expose the glottis for visualization and subsequent manual insertion of an endotracheal tube is called endotracheal intubation.
A conventional laryngoscope is an optical instrument having a rigid blade and a focused light source adapted to illuminate the region immediately beyond the blade tip. During laryngoscopy the patient is supine with the neck fully extended and the top of the head at the edge of the support surface. The laryngoscopist stands over the patient viewing the face as the tip of the blade is passed into the pharynx. Gentle upward traction is applied to the base of the tongue to lift it off the posterior surface of the pharynx and to expose the vocal cords and glottic opening. Thereafter, endotracheal intubation may be manually effected. More specifically, with the oropharyngeal passage clearly viewed with laryngoscopic techniques, the endotracheal tube may be inserted by grasping its proximal end and pushing it along side the laryngoscope blade into the trachea.
Typically, during intubation, the left hand of the doctor manipulates the laryngoscope and the right hand carefully threads the endotracheal tube through the oropharynx, passing the tube between the vocal cords and into the larynx and trachea. Anatomically, individual oropharyngeal channels vary greatly from patient to patient in size, shape and distensibility. Direct visualization is often difficult, and indeed in many cases the requisite exposure cannot be obtained by the laryngoscopist alone without assistance of another person who manipulates the larynx by the application of external pressure on the neck over the Adam's Apple. On occasion, the glottic opening may be viewed, but the laryngoscopist cannot maneuver the long (approximately 12 inches) plastic endotracheal tube through the narrow, curved and often quite still anatomical path.
Over the years lighted laryngoscopic blades have evolved into a myriad shapes and forms in an attempt to facilitate endotracheal intubation. Representative of the state of art are U. S. Pat. Nos. 4,793,327 for ENDOTRACHEAL INTUBATION DEVICE; 4,825,858 for AUTOMATIC INTUBATION DEVICE FOR GUIDING ENDOTRACHEAL TUBE INTO TRACHEA; 4,827,910 for LARYNGOSCOPE; 4,850,340 for ENDOTRACHEAL TUBE APPARATUS AND METHOD; 4,838,245 for INSTRUMENT FOR THE INSERTION OF ANESTHETIC CATHETERS; 4,884,558 for LARYNGOSCOPE ASSEMBLY INCLUDING DISPOSABLE PROTECTIVE ENCLOSURE; 4,905,669 for LARYNGOSCOPE; 4,947,829 for MODULAR BLADE LARYNGOSCOPE; and 4,947,896 for LARYNGOSCOPE. Despite the evolution of specialized instrumentation and advanced techniques, endotracheal intubation always requires considerable skill, often requires two persons, and on occasion cannot even be accomplished.